The elephants of Gash-Barka, Eritrea: nuclear and mitochondrial genetic patterns.

Eritrea has one of the northernmost populations of African elephants. Only about 100 elephants persist in the Gash-Barka administrative zone. Elephants in Eritrea have become completely isolated, with no gene flow from other elephant populations. The conservation of Eritrean elephants would benefit from an understanding of their genetic affinities to elephants elsewhere on the continent and the degree to which genetic variation persists in the population. Using dung samples from Eritrean elephants, we examined 18 species-diagnostic single nucleotide polymorphisms in 3 nuclear genes, sequences of mitochondrial HVR1 and ND5, and genotyped 11 microsatellite loci. The sampled Eritrean elephants carried nuclear and mitochondrial DNA markers establishing them as savanna elephants, with closer genetic affinity to Eastern than to North Central savanna elephant populations, and contrary to speculation by some scholars that forest elephants were found in Eritrea. Mitochondrial DNA diversity was relatively low, with 2 haplotypes unique to Eritrea predominating. Microsatellite genotypes could only be determined for a small number of elephants but suggested that the population suffers from low genetic diversity. Conservation efforts should aim to protect Eritrean elephants and their habitat in the short run, with restoration of habitat connectivity and genetic diversity as long-term goals.

A proboscidean from the late Oligocene of Eritrea, a "missing link" between early Elephantiformes and Elephantimorpha, and biogeographic implications.

We report on a late Oligocene proboscidean species from Eritrea, dated to 26.8 +/- 1.5 Mya. This "missing link" between early elephantiformes and Elephantimorpha is the oldest known nongomphothere proboscidean to probably display horizontal tooth displacement, typical of elephants [Elephantimorpha consists of Mammutida (mastodons) and Elephantida, and Elephantida includes gomphotheres, stegodons, and elephants]. Together with the newly discovered late Oligocene gomphotheres from Chilga, Ethiopia, the Eritrean taxon points to the importance of East Africa as a major area for the knowledge of the early evolution of Elephantimorpha before the faunal exchange between Eurasia and Africa.

Elephant brain. Part I: gross morphology, functions, comparative anatomy, and evolution.

We report morphological data on brains of four African, Loxodonta africana, and three Asian elephants, Elephas maximus, and compare findings to literature. Brains exhibit a gyral pattern more complex and with more numerous gyri than in primates, humans included, and in carnivores, but less complex than in cetaceans. Cerebral frontal, parietal, temporal, limbic, and insular lobes are well developed, whereas the occipital lobe is relatively small. The insula is not as opercularized as in man. The temporal lobe is disproportionately large and expands laterally. Humans and elephants have three parallel temporal gyri: superior, middle, and inferior. Hippocampal sizes in elephants and humans are comparable, but proportionally smaller in elephant. A possible carotid rete was observed at the base of the brain. Brain size appears to be related to body size, ecology, sociality, and longevity. Elephant adult brain averages 4783 g, the largest among living and extinct terrestrial mammals; elephant neonate brain averages 50% of its adult brain weight (25% in humans). Cerebellar weight averages 18.6% of brain (1.8 times larger than in humans). During evolution, encephalization quotient has increased by 10-fold (0.2 for extinct Moeritherium, approximately 2.0 for extant elephants). We present 20 figures of the elephant brain, 16 of which contain new material. Similarities between human and elephant brains could be due to convergent evolution; both display mosaic characters and are highly derived mammals. Humans and elephants use and make tools and show a range of complex learning skills and behaviors. In elephants, the large amount of cerebral cortex, especially in the temporal lobe, and the well-developed olfactory system, structures associated with complex learning and behavioral functions in humans, may provide the substrate for such complex skills and behavior.

Elephants and human color-blind deuteranopes have identical sets of visual pigments.

Being the largest land mammals, elephants have very few natural enemies and are active during both day and night. Compared with those of diurnal and nocturnal animals, the eyes of elephants and other arrhythmic species, such as many ungulates and large carnivores, must function in both the bright light of day and dim light of night. Despite their fundamental importance, the roles of photosensitive molecules, visual pigments, in arrhythmic vision are not well understood. Here we report that elephants (Loxodonta africana and Elephas maximus) use RH1, SWS1, and LWS pigments, which are maximally sensitive to 496, 419, and 552 nm, respectively. These light sensitivities are virtually identical to those of certain "color-blind" people who lack MWS pigments, which are maximally sensitive to 530 nm. During the day, therefore, elephants seem to have the dichromatic color vision of deuteranopes. During the night, however, they are likely to use RH1 and SWS1 pigments and detect light at 420-490 nm.

The elephants of Zoba Gash Barka, Eritrea: part 4. Cholelithiasis in a wild African elephant (Loxodonta africana).

A 4.0-kg cholelith was found within the abdominal cavity of a dead wild African elephant (Loxodonta africana) in Eritrea. Analysis of this cholelith by histochemistry, electron microscopy, electrospray mass spectroscopy, and energy-dispersive x-ray spectroscopy revealed it was composed of bile alcohols but no calcium, bilirubin, or cholesterol. Bacteria were also found in the cholelith. Similar, but smaller, bile stones have been identified previously in other wild African elephants and an excavated mammoth (Mammuthus columbi). Choleliths have been reported only once in a captive Asian elephant (Elephas maximus). Elephants, along with hyraxes (Procavia capensis) and manatees (Trichechus manatus), are unique among mammals in producing only bile alcohols and no bile acids, which may predispose them to cholelithiasis, particularly in association with bacterial infection. Dietary factors may also play an important role in cholelith formation.